Faucets having a single handle for adjusting both water flow rate and water temperature are well known. In such faucets, the handle is lifted upward to adjust water flow, and is moved from side to side to adjust hot and cold water proportions such that a desired overall temperature is achieved. Generally, the handle has approximately 180 degrees of freedom, such that only cold water from a cold water source is dispensed when the handle is at its rightmost position, and only hot water from a hot water source is dispensed when the handle is at its leftmost position. When the handle is located between these two extreme positions, a mixture of hot and cold water is dispensed.
One problem with this type of single-handle faucet is that at least some water is drawn from the hot water source in every operative position of the faucet handle except the extreme right. As a result, even though the operator may require only cold water, if he or she lifts the handle without first moving it to the extreme right, or neglects to move the handle to the right after lifting, at least some hot water from the hot water source will be used. The amount of hot water wasted in a given water drawing incident will be directly proportional to the handle position and the duration of time the handle is not turned to the extreme right. The cumulative effect of multiple incidents of this type, as may occur, for example, when the operator is running a garbage disposal or rinsing dishes while loading a dish washer can be a substantial waste of energy.
Also, if drinking water is being drawn and the faucet handle is in any position other then the extreme right, at least some hot water will be drawn and consumed. This water may not be safe for consumption since it may have been stagnant in a sediment laden tank for a substantial amount of time.
The need has therefore arisen for a single handled faucet that draws water from a hot water source only if an operator specifically requests hot water and then functions as a conventional single handle faucet for the duration of use.